Driving assistance display apparatus has been in widespread use that provides the driver with the view at the rear of a vehicle without the driver looking into a rearview mirror, by mounting a vehicle-mounted camera, e.g. on the rear trunk of a vehicle, in a rear direction and presenting the image acquired from the vehicle-mounted camera to the driver. Some of such driving assistance display apparatus converts a real image from a vehicle-mounted camera to an image from a virtual viewpoint and display the image on a monitor. Such driving assistance display apparatus is used to assist safety in backing a vehicle and parking.
FIG. 3 shows a block diagram of a general driving assistance display apparatus. The driving assistance display apparatus includes a camera 2 mounted on a vehicle 1, image synthesis/conversion device 3 for processing an image shot by the camera 2, and a monitor 4 for displaying an image acquired after the image synthesis/conversion processing.
The camera 2 is mounted to shoot the rear of the vehicle 1. An image acquired by the camera 2 has undergone processing to remove lens distortion by the image synthesis/conversion device 3 and is converted to an image as if shot from an arbitrary virtual viewpoint and displayed on the monitor 4.
FIG. 4 is an input image to the camera 2. FIG. 5 shows an image acquired by setting a virtual viewpoint over the vehicle 1 and converting a real image to an image of the rear of the vehicle from the virtual viewpoint. An image shown in FIG. 4 is an image shot by the camera 2 as a wide angle camera without conversion. Thus the rear bumper image 5 that is actually a straight line is distorted. A guide line 6 is superimposed at the same time. The guide line 6 includes a vehicle passing guide line 7 indicating the vehicle width (body line) and a distance guide lines 8 indicating the distance from the rear of the vehicle on the road surface.
FIG. 5 shows an image acquired by viewpoint-converting the image in FIG. 4 to be seen from a virtual viewpoint. A rear bumper image is converted to a straight line image 5a. A vehicle passing guide line 7a and a distance guide lines 8a of a guide line 6a are also displayed as straight line images on the monitor 4. The driver watches the image in FIG. 5 on the monitor as he/she parks the vehicle. While a single vehicle-mounted camera is used in the example of FIG. 3, it is possible to synthesize images from a plurality of cameras and display the resulting image on the monitor.
In the conventional driving assistance display apparatus, the same screen is used to implement the procedures including safety check and parking. An image with a wide field of view of the rear of a vehicle is appropriate for safety check, while an image from a virtual viewpoint in the close proximity of a vehicle is advantageous for parking assistance. In this way, suitable images differ with purposes.
In the case of parking assistance also, an image of a wide field of view is required in order to grasp the global situation around a vehicle thus guiding the vehicle to its parking space in the initial stage of parking. In the final stage of parking, only a limited area around the vehicle must be grasped for alignment. As such, the optimum image depends on the stage of parking although a same operation procedure.
Representing an image of a wide field of view to the driver when it is necessary to grasp only a limited area around the vehicle adds to the distortion of a three-dimensional object caused by viewpoint conversion. This is impractical because it leads to a sense of incongruity in the parking procedure or failure to recognize the three-dimensional object.
To offset this, for example at least in the conventional parking procedure, an image of a wide field of view required in the initial stage of parking is switched to an image of a limited area around the vehicle as necessary. However, switching of images in the sequence of parking operation obliges the driver to understand the correspondence between images before and after the switching, which is not very favorable.
For resolving the above problem, the invention aims at providing driving assistance display apparatus that enables the driver to check safety of the rear of the vehicle and grasp the limited area around the vehicle in the final stage of parking without switching screens.